The problems the invention deals with can be explained most obviously in conjunction with high-speed data transmission cables, which does however not restrict the use of the invention to this purpose.
Customary data transmission cables use several of the above twisted pairs, for example four, which must be screened as the category of transmission bandwidth and transmission quality rises. External screening of the twisted pairs as well as screening of the twisted pairs one in relation to the other in a cable are important in this case.
For corresponding specifications of transmission bandwidth and transmission quality to be obtained, U.S. Pat. No. 6,624,359 B2 teaches to provide the twisted pairs with a screening sheet which is comprised of a laminate of a plastic-material substrate layer lined with a screening layer of metal. This document further shows the most varying configurations of how to fold this laminated sheet so that it forms an external screening envelope placed around several twisted pairs and for instance an internal separating and supporting structure of star configuration. Fundamentally, the screening sheet is designed as a strip of material having a continuous screening layer, for example of aluminum or copper, in the longitudinal direction of the strip.
The above design of an electrically conductive screening layer that is continuous in the longitudinal direction of the cable gives rise to problems of grounding because, given varying potentials at the ends of a line, high potential compensation currents can flow through the screening. They cause malfunction and possibly even damages of equipment connected to such a data transmission cable.